使用RegisterAssemblyTypes时如何使用Autofac注册装饰器？

Question

这是我的代码

public interface ICommandHandler<T> 
{ 
    void Handle(T command); 
} 

public class CreateUserCommandHandler : ICommandHandler<CreateUserCommand> 
{ 
    public void Handle(CreateUserCommand command) 
    { 
     // do something with the command 
    } 
} 

public class LoggingCommandDecorator<TCommand> : ICommandHandler<TCommand> 
{ 
    private readonly ICommandHandler<TCommand> _commandHandler; 

    public LoggingCommandDecorator(ICommandHandler<TCommand> commandHandler) 
    { 
     _commandHandler = commandHandler; 
    } 

    public void Handle(TCommand command) 
    { 
     Debug.WriteLine("Logging..."); 

     _commandHandler.Handle(command); 
    } 
} 

这里是我的注册：

private void SetupAutofac() 
{ 
    var builder = new ContainerBuilder(); 

    // Register your MVC controllers. 
    builder.RegisterControllers(typeof(WebApiApplication).Assembly); 

    // OPTIONAL: Register model binders that require DI. 
    builder.RegisterModelBinders(Assembly.GetExecutingAssembly()); 
    builder.RegisterModelBinderProvider(); 

    var assemblies = AppDomain.CurrentDomain.GetAssemblies(); 
    builder.RegisterAssemblyTypes(assemblies) 
      .As(o => o.GetInterfaces() 
      .Where(i => i.IsClosedTypeOf(typeof(ICommandHandler<>))) 
      .Select(i => new KeyedService("Handler", i))); 

    builder.RegisterGenericDecorator(typeof(LoggingCommandDecorator<>), 
          typeof(ICommandHandler<>), 
          "Handler", "DecoratedHandler"); 


    var container = builder.Build(); 

    DependencyResolver.SetResolver(new AutofacDependencyResolver(container)); 
} 

当我运行这段代码，我得到以下异常：

建设者没有发现 可以使用0123调用'Autofac.Core.Activators.Reflection.DefaultConstructorFinder'类型 'AspectDemo.Controllers.HomeController'可用服务和参数：无法解析参数 'AspectDemo.Business.ICommandHandler 1[AspectDemo.Business.Users.CreateUserCommand] createUserHandler' of constructor 'Void .ctor(AspectDemo.Business.ICommandHandler 1 [AspectDemo.Business.Users.CreateUserCommand]）'。

当我使用以下作为我的注册，我没有得到异常，但我也没有任何装饰。

builder.RegisterAssemblyTypes(assemblies) 
     .AsClosedTypesOf(typeof(ICommandHandler<>)) 
     .AsImplementedInterfaces(); 

我该怎么做才能使用装饰器？

注：现在我只是使用一个装饰器，但最终我认为我有大约4-5个装饰器。

Answer 1

当您使用RegisterGenericDecorator方法的toKey参数，它导致了一个名为注册，所以你必须要解决的一个名为ICommandHandler

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Handler", 
    toKey : "DecoratedHandler"); 

然后你就可以解决这个问题是这样的：

container.ResolveKeyed<ICommandHandler<CreateUserCommand>>("DecoratedHandler"); 

toKey参数是可选的：

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Handler"); 

然后你就可以解决这个问题是这样的：

container.Resolve<ICommandHandler<CreateUserCommand>>(); 

的toKey是有用的，当你有中间装饰：

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Original", 
    toKey : "Logging"); 

builder.RegisterGenericDecorator(
    typeof(AuthorizationCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Logging"); 

在这种情况下，ICommandHandler<CreateUserCommand>将LoggingCommandDecorator<>和AuthorizationCommandDecorator<>